A. Field of the Invention
The present invention generally relates to a device for supporting an occupant in a seated position, and in one preferred embodiment, to a chair of the reclining back type. In a further preferred embodiment, the present invention relates to a chair having a resistance to tilting that automatically adjusts in proportion to the weight of the user and the tilt angle.
B. Description of the Related Art
Reclining type chairs commonly used in offices typically provide for the back support to recline alone, for the seat and back support to recline as a unit, or for the back support to recline in a coordinated proportion with the seat. If the back support alone pivots, it generally creates a problem known as “shirttail pull.” This problem is particularly acute if the pivot of the chair back support is not coordinated with the natural body action of the occupant. This problem can also be accentuated by the tendency of the hips of the occupant to slide forward as the back support tilts rearwardly.
In chairs where both the seat and back recline as a unit, in the reclined position there is a tendency to lift the legs of the occupant from the floor, which creates an undue pressure by the forward edge of the seat against the underside of the legs of the occupant immediately above the knee. To overcome this problem, the pivot point of the reclining action may be moved forward sufficiently to permit the occupant's feet to remain on the floor. One undesirable effect of this arrangement is that the body angle between the occupant's torso and his legs is unchanged, and as a result, the occupant's eye level drops undesirably when the chair is reclined.
In any reclining chair, it is desirable that the recline pivot point be at the center of the body or where the occupant's back normally pivots (i.e., an axis through the user's hip joints). However, the pivot point of a reclining chair is normally displaced from the ideal pivot point. It is also desirable to have a chair wherein the angle between the occupant's torso and his legs opens up to relieve internal congestive body pressures. It is further desirable to provide a chair wherein the user's feet remain on the floor and the recline action parallels the natural body action closely enough to avoid the common shirttail pull problem.
Therefore, it is also desirable to provide a chair of simple, economical construction that lends itself to high production manufacturing and fabrication procedures, and yet of clean, pleasing appearance emphasizing the isolated and separate appearance of the seat and back support with respect to the supporting frame and base.
U.S. Pat. No. 4,429,917 to Diffrient allegedly reports a chair with a four bar non-parallel linkage mechanism to obviate many of these problems. Likewise, U.S. Pat. No. 4,943,114 to Piretti allegedly reports a chair with a compact backrest linkage mechanism that enables the chair back support and seat to recline. U.S. Pat. No. 5,251,958 to Roericht et al. allegedly reports a chair with a synchronous adjusting device that uses the weight of the user to provide a restoring force to return the chair back support to an upright position after a user has reclined in the chair. U.S. Pat. No. 5,486,035 to Koepke, et al., asserts, without providing any showing, that “[i]n such constructions, the difficulty of reclining the chair, i.e., generating the reclining force, increases the further the chair is reclined, and it is common to employ adjusting apparatus for increasing or decreasing the reclining tension of a chair, such adjusting apparatus changing the tension of a spring, or otherwise modifying the reclining mechanism” (col. 1, 11. 29-34).
Moreover, while it is believed that some reclining chairs heretofore available have had a means to adjust their resistance to reclining, such adjustments have been less than ideal, very cumbersome or not practicable to an occupant. Instead, rather than confront the processes necessary to adjust their chairs to fit the needs of their particular body build, most occupants of chairs use them without making any adjustments. Consequently, any ergonomic advantages that might be delivered by the properly tuned chair are not achieved. Thus, there remains a need for a chair that is adjustable to the needs of the individual chair occupant without requiring any substantial effort on the occupant's part to effect the adjustments—in other words, a substantially self-adjusting ergonomic chair.